Lots of folks are afraid of live macro because some of them (typically a couple of the fast-growing
Caulerpa species) can "go sexual" and release gametes into the tank. We actually let this happen once just to see what happened in terms of the tank dying, yadda-yadda. It was nothing that some carbon and a WC couldn't fix, and we lost no livestock. However, the macro will "tell" you if it's about to go south by going milky and having green spots on it (the gametes).
What this phenomenon is all about is a last ditch effort by the macro to survive poor conditions, such as temp swings, overgrowth ("smothering" itself), over-pruning, inability to compete with other macros for food, etc. So...it releases gametes into the water column that will float away from the "bad" area, and begin life in a more habitable area.
One reason you may not want them in the reef DT is that they could overgrow corals if not kept pruned.
We currently run 13 FOWLR setups of various sizes and bioloads, and the macro really goes a long way in helping with water quality. They use ammonia first, thus preventing them from becoming nitrates, but will also use nitrates, and even phosphates. If you run them in your sump and light them on a reverse schedule than your DT, they will aid in stabilizing the nightly pH drops since the system never truly goes into normal respiration as photosynthesis never stops.
They also harbor pods which most fish really find tasty.
Finally, I think they look super and add some nice movement to the DT:
